Analysis of linear Phase-Locked Loops in Grid connected Power Converters Steinkohl, Joachim; Wang, Xiongfei; Davari, Pooya; Blaabjerg, Frede-Department of Energy Technology, Aalborg University

 

Analysis of linear Phase-Locked Loops in Grid-Connected Power Converters Joachim Steinkohl, Xiongfei Wang, Pooya Davari and Frede Blaabjerg Aalborg University 

 Abstract

 Fast and accurate synchronization capability of grid-connected converters is becoming more and more important to ensure proper performance during transient events, such as grid faults. The higher requirements during the operation, as Fault-Ride-Through with reactive current injection, cause higher requirements on the operation during severe system conditions. This paper analyzes an addition to Synchronous-Reference-Frame Phase-Locked Loops for power electronic converters, that is linearizing the input signal. This enhances the tracking capabilities during abnormal transient events in the power grid. The improved control is analyzed and its increased performance is validated through simulations and experimental results.

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https://vbn.aau.dk/files/319223001/Analysis_of_linear_Phase_Locked_Loops_in_Grid_Connected_Power_Converters.pdf

Small-Signal Stability Analysis and Optimization of Grid-Forming Permanent-Magnet Synchronous-Generator Wind Turbines by Guanghui Li ,Runqi Han ,Zhen Li,Bin Lui,

Small-Signal Stability Analysis and Optimization of Grid-Forming Permanent-Magnet Synchronous-Generator Wind Turbines by Guanghui Li 1,Runqi Han 2,*,Bin Liu 2,*ORCID andZhen Li 3ORCID National Key Laboratory of Renewable Energy Grid-Integration, China Electric Power Research Institute, Beijing 100192, China College of Artificial Intelligence, China University of Petroleum (Beijing), Beijing 102249, China School of Automation and Key Laboratory for Intelligent Control & Decision on Complex Systems, Beijing Institute of Technology, Beijing 100081, China 

 Abstract Due to the ability to improve the low-inertia characteristics of power systems and offer reliable voltage and frequency support, grid-forming permanent-magnet synchronous-generator wind turbines (PMSG-WTs) based on virtual synchronous-generator (VSG) technology are emerging se the direction for future developments. Previous studies on the small-signal stability of grid-forming PMSG-WTs that connect to the grid usually simplify them into grid-connected grid-side converters (GSC), potentially leading to errors in stability analyses. Therefore, this paper considers the machine-side converter (MSC) control and establishes impedance models for grid-forming PMSG-WTs. Based on the sensitivity calculation of controller parameters using symmetric difference computation based on zero-order optimization, the impact of the internal controller on outside impedance characteristics is quantitatively analyzed. Additionally, an optimization method to enhance the stability of a hybrid wind farm by adjusting the ratio of grid-forming and grid-following wind turbines is proposed.

LINK : https://www.mdpi.com/1996-1073/17/18/4560

Stability analysis of small signals under different ratios of grid-following to grid-forming converters sent via flexible DC delivery-Feng Li1, Zhijie Li2,*, Shuangmian Yang1, Jinyu Wang2 and Yibo Zhang1 1TBEA Science & Technology Investment Co., Ltd., Tianjin, 301700, China 2College of Electrical Engineering, Xi'an Jiaotong University, Xian, Shanxi, 712000, China

 Stability analysis of small signals under different ratios of grid-following to grid-forming converters sent via flexible DC delivery Feng Li1, Zhijie Li2,*, Shuangmian Yang1, Jinyu Wang2 and Yibo Zhang1 1TBEA Science & Technology Investment Co., Ltd., Tianjin, 301700, China 2College of Electrical Engineering, Xi'an Jiaotong University, Xian, Shanxi, 712000, China 

 Abstract: Under the "dual carbon" strategy, frequent wide-band grid oscillations caused by grid-following converters as the interface for renewable energy integration have become common. Existing studies suggest that the addition of grid-forming converters can address this issue, but few explain the reasons from a stability mechanism perspective. Additionally, most studies overlook the interaction between converters and sending-end converter stations. This paper first conducts sequential impedance modeling. Then, based on impedance network analysis, it examines the impact of sending-end converter stations on stability assessment. Finally, by adjusting the grid-following/grid-forming ratio, Nyquist curves under different ratios are generated to analyze the mechanism by which grid-forming converters enhance gridfollowing small-signal stability. Corresponding simulation models are also developed for validation.

LINK: https://iopscience.iop.org/article/10.1088/1742-6596/2896/1/012028

A Study on Internal Fault Simulation Methods for 345kV Autotransformers 345kV 단권변압기 내부고장 모의방법에 관한 연구 Jong-Kee Choi ․ You-Jin Lee ․ Jun-Ho Cho ․ Young-Hun Kwon ․ Ji-Hwan Park ․ Young-Hun Jang 최종기† ․ 이유진* ․ 조준호** ․ 권영훈*** ․ 박지환§ ․ 장영훈

 

SCHEMATIC DIAGRAM THREE-PHASE PHASE FAILURE DETECTOR CIRCUIT AND THREE-PHASE PHASE SEQUENCE-Simulation and Analysis Using PSpice